Genetically-predicted physical activity levels are associated with lower colorectal cancer risk: a Mendelian Randomization Study

Xiaomeng Zhang, Evropi Theodoratou, Xue Li, Susan M Farrington, Philip J Law, Peter Broderick, Marion Walker, Yann C Kimentidis, Jessica Rees, Richard S Houlston, Ian P.M. Tomlinson, Stephen Burgess, Harry Campbell, Malcolm G Dunlop, Maria Timofeeva

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

We conducted a mendelian randomisation (MR) study to investigate whether physical activity (PA) causes a reduction of colorectal cancer risk and to understand the contributions of effects mediated through changes in body fat.
Common genetic variants associated with self-reported moderate-to-vigorous PA (MVPA), acceleration vector magnitude PA (AMPA) and sedentary time were used as instrumental variables. To control for confounding effects of obesity, we included instrumental variables for body mass index (BMI), body fat percentage, waist circumference and arm-, trunk- and leg-fat ratios. We analysed the effect of these instrumental variables in a colorectal cancer genome-wide association study comprising 31 197 cases and 61 770 controls of European ancestry by applying two-sample and multivariable MR study designs.
We found decreased colorectal cancer risk for genetically-represented measures of MVPA and AMPA that were additional to effects mediated through genetic measures of obesity. Odds ratio and 95% confidence interval (CI) per standard deviation increase in MVPA and AMPA was 0.56(0.31,1.01) and 0.60(0.41,0.88) respectively. No association has been found between sedentary time and colorectal cancer risk. The proportion of effect mediated through BMI was 2%(95%CI:0%,14%) and 32%(95%CI:12%,46%) for MVPA and AMPA respectively.
These findings provide strong evidence to reinforce public health measures on preventing colorectal cancer that promote physical activity at a population level regardless of body fatness.
Original languageEnglish
JournalBritish Journal of Cancer
Early online date29 Jan 2021
Publication statusE-pub ahead of print - 29 Jan 2021


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